Twine tension controlling devices



1962 J. J. MULVEY ETAL 3,051,412

TWINE TENSION CONTROLLING DEVICES Filed Feb. 13, 1961 F 1 i thei Attamey United States 3,051,412 TWINE TENSION CONTROLLING DEVICES John J. Mulvey and Lionel W. G. Wilkinson, Leicester,

Leicestershire, England, assignors to United Shoe Machinery Corporation, Boston, Mass, a corporation of New Jersey Filed Feb. 13, 1961, Ser. No. 88,751 Claims priority, application Great Britain May 18, 1960 3 Claims. (Cl. 242l29.2)

This invention relates to improvements in devices for strand feeding and tensioning, and in particular it relates to devices wherein it is necessary to maintain an optimum degree of tension throughout a length of strand as the strand is being drawn out from a source of strand supply and mechanically applied as a wrapping for tying up bundles.

There are several types of automatic bundle tying machines during the operation of which the bundle reposes upon a work table so located that the bundle is encircled by a rotatable ring provided with a strand or twine engaging gripper adapted to clamp the free end of the twine. Thus, when the ring is rotated about the bundle, a length of twine will be withdrawn from the supply and entrained about the bundle to form a wrapping which, if the twine is maintained under proper tension, may be tied or otherwise secured to form a tight bundle. As one example, such a bundle tying machine is disclosed in United States Letters Patent No. 2,198,440, issued April 23, 1940 in the name of Marchand.

Since the ring diameter for any given tying machine cannot be adjusted in accordance with the various shapes and sizes of the bundles that are to be wrapped, there is a constant minimum length of twine that must be drawn out from the source of supply during each rotation of the twine gripper around a bundle. Therefore, in the case of relatively small bundles the length of twine required initially to be withdrawn by the gripper may greatly exceed the amount necessary to complete the wrapping. In addition, there are many other factors that momentarily may produce an excess amount of twine feed which, if not quickly retracted by a slack take-up mechanism, would cause a faulty operation of the tying machine.

A conventional slack take-up and strand tensioning device commonly employed comprises a friction device in which the strand is gripped under an adjustable spring pressure, and a slack take-up arm, which is movable between an upper position and a lower position and is urged toward its lower position by a weight. After the strand is withdrawn through the friction device it passes under the take-up arm, which is held by strand tension in its upper position while strand is being drawn into the machine, but the slack take-up arm drops into its lower position whenever slack is developed in the strand. It will be realized that the tension imparted to the strand by the adjustable spring must be greater than that which would allow the take-up arm to drop into its lower position, otherwise the take-up arm will not be in its up positionrwhen it is required to take up slack. Such a device is subject to certain disadvantages, particularly when a comparatively small bundle is being operated upon, because it is necessary that a large amount of slack be taken up Very quickly if an adequately tight tie is to be achieved. To accomplish this it is necessary 3,051,412 Patented Aug. 28, 1962 "ice to have a heavy weight on the take-up arm, and this heavy weight necessitates increasing the tension imparted by the adjustable spring pressure. Under such circumstances, the spring pressure required is excessively high, and results in damage to the strand, especially if the latter be of twine such as sisal. Further, when the machine, with the slack take-up device in adjustment for small bundles, is used for large bundles, which may well occur if a run of bundles of different sizes is to be dealt with, excessive tension may occur in the twine around such a large bundle.

Accordingly, it is the object of this invention to provide a twine tensioning and slack take-up device wherein a uniform optimum degree of tension is always maintained without regard to whether twine is being drawn into the machine, or is being retracted back out of the machine by operation of the slack take-up arm.

A further object is to provide a quick acting slack take-up mechanism that, during the feeding operation, will normally be in position promptly to take up slack, even when a relatively light tension is to be maintained on the twine.

The present invention provides as one of its several features a tensioning device for twine comprising a slack take-up arm which is movable between an upper and a lower position, and a twine feed control device which normally is arranged to snub the twine and allow the passage of twine through it only when the slack take-up arm is in its upper position.

Other objects and advantages of the invention will be apparent from the following detailed description when considered in conjunction with the accompanying drawmgs.

In the drawings:

FIG. 1 is an elevation partially section, showing a twine tension controlling device, constructed in accordance with this invention, with the slack take-up arm in a lower position and with the twine snubbing mechanism in position to prevent strand feed from the twine supply; and

FIG. 2 is an elevation partially section, showing the slack take-up arm in an elevated position and the snubbing mechanism shifted to the strand feeding position.

While the device about to be described with reference to the drawings is particularly well adapted for employment in conjunction with a machine for tying bundles with twine, this device may be employed to equal advantage in other types of machines wherein lengths of strand that are drawn into the machine must be kept under a controlled degree of constant tension. Therefore, the scope of this invention is not to be limited in any way by the particular machine with which it is to be employed; also, it is immaterial whether the strand employed be twine or some other tying medium. Accordingly, no machine for consuming the twine has been illustrated; and the inter-relation of this device (with any machine has been indicated merely by a legend designating that the direction of strand feed into a machine is toward the righthand side of FIG. 1. Also, indicated by legend only, is the fact that any suitable source of strand supply may be provided to lead the strand into the left-hand side of the illustrated device.

In the drawings, the twine tension controlling device comprises a slack take-up arm 10 which is movable between-an upper position (FIG. 2) and a lower position (FIG. 1), and a twine snubbing mechanism, designated generally by the arrow S, which is arranged to allow the passage of twine through it only when the slack take-up arm is in its upper position.

The twine snubbing device S comprises a bracket 12, fixed to the frame of a machine, on which bracket is pivoted, at 14, a Z-shaped lever member 16. The member 16 comprises a downwardly extending cam arm 18 having a cam surface 26 and an upwardly extending arm 22 in which a twine snubbing roll 24 is freely mounted on a pin 26. The lever member 16 is urged in a counterclockwise direction about its pivot 14 by a spring 28 which acts yieldably between the pin 26 and the frame of the machine. The upper peripheral portion of the roll 24 lies in a close fitting channel 30 formed in the bracket 12. The channel 30 is formed in part by a stop member 32 against which a face 34 of the arm 22 may abut under the action of the spring 28. The cam arm 18 is mounted for slidable adjustment on the arm 22 by a tongue 36, of the cam arm 18, that fits into a corresponding groove in the arm 22, and a screw 38 passes through a slot 40 in the arm 22 and is screwed into the arm 18. When the screw 38 is slackened, the relative positions of the two arms 18 and 22 may be adjusted by moving the tongue 36 in its groove, and then tightening the screw to maintain the two arms in adjusted position.

The slack take-up arm of the twine tension controlling device is pivoted at 42 to a bracket 44 fixed to the frame of the machine. Two stop members 46, 48 limit movement of the slack take-up arm 10 about its pivot. Mounted on the arm 10 are a biasing weight 50 and a twine receiving guide roll 52 which is freely rotatable on a pin 54 and is disposed in the plane of the roll 24. The free end of the arm 10 is formed as a cam end portion 56, which, when elevated, is adapted to engage with the cam surface 20 on the twine snubbing mechanism. Also mounted on the bracket 12 are two guide rolls, a first roll 58 in the plane of the rolls 24 and 52, and a second roll 60 perpendicular to the plane of the other three rolls.

When a machine, equipped with this twine tension controlling device, is in use, twine T passes from a source of supply (not shown) into the channel 30, over the snubbing roll 24, under the roll 52, over the roll 58, and around the roll 60 into the machine.

In the at-rest condition of the device, the slack takeup arm 10 is approximately in the position shown in FIG. 1, whereat the twine T is gripped tightly between the snubbing roll 24 and the channel 30 so that twine, even under heavy tension, cannot be drawn therebe-tween to pass into the loop of twine extending between the rolls 24 and 58. Still referring to the position of the device as illustrated in FIG. .1, the slack take-up arm 10, which is always biased downwards by its weight 50 to impart tension to the twine, is in an intermediate position indicating that some twine slack has just been taken up by retracting the twine from the machine and drawing it into the loop extending between the rolls 24 and 58. If, incidental to the machine operation, more slack were now to occur in the length of twine extending in the direction of twine feed into the machine, this additional slack would quickly be taken up by force of the weight 50 which would draw more twine from the machine side into the loop, thus allowing the arm 10 to move to a lower position. Referring now to the snubbing mechanism S, it is seen that the pivot point 14 is so located that there is insufficient clearance to allow the snubbing roll 24 to be forced in an anticlockwise direction through the channel 30; but the force of the spring 28 tends to hold the roll in a twine jamming position wherein a monkey bite is applied to the twine leading into the loop from the twine supply side. It is also seen that, due to the offset position of the pivot point 14 with respect to the right-hand side of the roll 24, over which the twine enters the loop, the downward force exerted by the weight of the arm 10 serves only to urge the snubbing mechanism counterclockwise into tighter gripping relationship with the twine in the channel 30. However, when the machine commences a bundle wrapping operation and twine begins to be drawn into the machine, the initial quantity of said twine is provided by a withdrawal from the loop which, as it is shortened, lifts the slack take-up arm to an elevated position (FIG. 2) wherein the cam end portion 56 of the arm abuttingly contacts the cam surface 20 on the cam arm 18. As twine continues to be pulled into the machine, the resultant upward movement of the cam end 56, pressing against the cam arm 18, shifts the snubbing mechanism in a clockwise direction against the force of the spring 28, thereby terminating the snubbing action of the roll 24 to permit the withdrawal of twine from the strand supply end of the loop. if, during this withdrawal from the twine supply, the tension in the twine leading to the machine decreases to a degree where it is insufficient to overcome the downward force of the slack take-up arm, said arm will immediately be lowered out of engagement with the cam arm 18, whereupon the snubbing mechanism S will again grip and stop the feed of twine from the supply end of the loop. Thus, from the foregoing description of the operation of the twine tension controlling device, it is apparent that while twine is steadily being drawn out from the loop by the machine, the slack take-up arm 10 will rock up and down slightly, and the snubbing mechanism will intermittently grip and release the twine coming from the supply end in order to control the tension of the twine leading to the machine in accordance with the tensioning force imparted by the weight 50 which may be adjusted, by shifting, to vary the tension as desired.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is:

1. A twine tension controlling device for use with a bundle tying machine wherein surplus portions of the twine which has been drawn into the machine must periodically be retracted from the machine in order to maintain a proper twin tension, said device comprising: a pivotally mounted slack take-up arm having a twine holding guide on the free end of said arm movable between an upper and a lower position; and a twine snubbing mechanism for controlling the passage of twine from the source of twine supply to said am, said mechanism being constructed and arranged to allow the passage of twine through it only when said arm is in its upper position.

2. A twine tension controlling device for use with a bundle tying machine wherein surplus portions of the twine which has been drawn into the machine must periodically be retracted from the machine in order to maintain a proper twine tension, said device comprising: twine snubbing mechanism operatively engageable with the twine adjacent a source of twine supply and shiftable from a twine gripping position to a twine feeding position; yieldable means normally urging said mechanism into the twine gripping position; a slack take-up arm having a twine receiving guide at one end of the arm engageable with the twine to form a looped portion of twine between the machine and said snubbing mechanism; biasing means tending to move said end of the arm in a direction away from the snubbing mechanism to lengthen the loop by drawing twine from either the machine or the twine supply side of the loop, said arm end being movable toward the mechanism in response to the twine drawing action of the machine during intervals when the tension thus imparted to the twine is suflicient to overcome the force of the biasing means; and cam means associated with the mechanism and disposed in the path of said arm for shifting the mechanism to the twine feeding position when the arm is moved by sufiicient twine tension into engagement with the cam means.

3. In a slack take-up and twine tensioning device for maintaining a predtermined degree of tension in a length of twine while the twine is being drawn into a machine, said device being operatively associated with the length of twine between the machine and a source of twine supply: a slack take-up arm having a twine receiving guide at one end of the arm engageable with a looped portion of the twine between the machine and the source of twine supply; biasing means tending to move said end of the arm in a direction to lengthen the loop by drawing twine from either side into the loop; shiftable twine snubbing mechanism engageable with the twine on the supply side of the loop, said mechanism normally being biased by yieldable means in a direction to apply a monkey bite hold on the supply side of the twine and thus prevent its being drawn into the loop; and cam means associated with the mechanism and disposed in the path of said arm for shifiting the mechanism out of snubbing relationship with the twine to permit twine to be drawn from the supply when the arm is moved by suflicient twine tension into engagement with the cam means.

References Cited in the file of this patent UNITED STATES PATENTS 819,521 Copcutt May 1, 1906 2,686,018 Courtney Aug. 10, 1954 

